From f5d47c079e4ed23d0aa2d2f2f4ce19ee720bee1b Mon Sep 17 00:00:00 2001
From: Pauli Virtanen <pav@iki.fi>
Date: Sun, 13 Feb 2022 15:08:52 +0200
Subject: [PATCH] conf: fix fork/execvp/waitpid usage

In context.exec after forking, if execvp returns we have to exit since
we're in the child process.

To avoid zombies, either SIGCHLD need to be handled/ignored, or
double-fork to create orphan processes. This is in library code, so it
seems best to just double-fork.
---
 src/pipewire/conf.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/pipewire/conf.c b/src/pipewire/conf.c
index 50bc7e471..2d82c44ca 100644
--- a/src/pipewire/conf.c
+++ b/src/pipewire/conf.c
@@ -734,6 +734,16 @@ static int do_exec(struct pw_context *context, const char *key, const char *args
 	if (pid == 0) {
 		char *cmd, **argv;
 
+		/* Double fork to avoid zombies; we don't want to set SIGCHLD handler */
+		pid = fork();
+
+		if (pid < 0) {
+			pw_log_error("fork error: %m");
+			exit(1);
+		} else if (pid != 0) {
+			exit(0);
+		}
+
 		cmd = spa_aprintf("%s %s", key, args ? args : "");
 		argv = pw_split_strv(cmd, " \t", INT_MAX, &n_args);
 		free(cmd);
@@ -745,13 +755,18 @@ static int do_exec(struct pw_context *context, const char *key, const char *args
 		if (res == -1) {
 			res = -errno;
 			pw_log_error("execvp error '%s': %m", key);
-			return res;
 		}
-	}
-	else {
+
+		exit(1);
+	} else if (pid < 0) {
+		pw_log_error("fork error: %m");
+	} else {
 		int status = 0;
-		res = waitpid(pid, &status, WNOHANG);
-		pw_log_info("exec got pid %d res:%d status:%d", pid, res, status);
+		do {
+			errno = 0;
+			res = waitpid(pid, &status, 0);
+		} while (res < 0 && errno == EINTR);
+		pw_log_debug("exec got pid %d res:%d status:%d", (int)pid, res, status);
 	}
 	return 0;
 }